The present invention relates generally to an actuator assembly in a disc drive, and more particularly to an actuator assembly having a bearing cartridge threadably mountable within an actuator body.
Generally, the disc drive used as an auxiliary memory device in a computer includes at least one disk which is rotated at a high speed by a spindle motor, and an actuator arm assembly having an actuator body and a bearing cartridge. The actuator body has at least one arm which rotates in response to a voice coil motor about a pivot point for moving a magnetic head at a distal end of each actuator arm. The magnetic head writes data onto the tracks of the disc and reads the data recorded on the tracks of the disc. The magnetic head moves in proximity to the disc, wherein the magnetic head is influenced by an airflow generated on a surface of the disc as the disc rotates at a high speed to maintain a minute gap between the magnetic head on the actuator arm and the disc.
Design requirements for actuator performance and positional accuracy for disc drives are continually becoming more stringent. In particular, the head disc assembly (HDA) is expected to survive extreme external shock events where the accelerations encountered often exceed 1000 g""s. Extensive experimental and design efforts has been expended to understand and improve the HDA performance associated with these extreme disturbances to the HDA such as those encountered during topple drop testing. It is known that the head stack assembly (HSA) including the actuator body and bearing assembly is a key component in the HDA. Improving the uniformity of the HSA is a primary key to overall enhancement of the HDA with regard the aforementioned shock events.
Several methods currently exist for integrating the bearing cartridge and the actuator body of the actuator assembly of the disc drive. One method does not include a bearing cartridge, but instead includes boding the bearings directly into a bore in the actuator body. The other method includes the use of the separate bearing cartridge where the bearings are first assembled and preloaded into a sleeve, which is then attached to the actuator body.
There are several techniques that exist for coupling the bearing cartridge to the actuator body, which meet the requirements of removeability necessary for rework of the actuator assembly, when necessary. Three of the most common are (1) a tolerance ring press fit, (2) set screws through the actuator body into the bearing cartridge, and (3) the use of a spring loaded snap ring. The technique of a tolerance ring press fit and set screws through the actuator body into the bearing cartridge are not widely used due to high manufacturing costs and increased unreliability.
Most of the current desktop products today are using the snap ring technique which provides the snap ring receivable within a groove in the bearing cartridge and acting against the actuator body to secure the bearing cartridge therein. Unfortunately, the snap ring techniques has several major disadvantage. In particular, with the snap ring technique, the bearing cartridge is not actually rigidly fixed to the actuator body. The resulting actuator assembly is essentially a spring-mass system that has a large variability due to the tolerances associated with the parts, especially the tolerance between the bearing cartridge and the actuator body. In addition, space available for assembling the actuator assembly with the snap ring technique is very limited thereby creating difficulties during manufacture of the HSA. Furthermore, to meet the high stiffness requirements of the actuator assembly, the spring rates for the snap ring are very high resulting in a actuator assembly design where the final actual spring preload can be highly sensitive to part tolerances and varies over a wide range.
A need therefore exists in the art for attaching a bearing cartridge to an actuator body that improves the interface between the actuator body and the bearing cartridge. It is desirable that this be achieved, moreover, without compromising the actuator assembly performance and the interface between the actuator body and bearing cartridge. The present invention solves these problems and offers other advantages over the prior art.
The present invention relates to an actuator assembly that has a bearing cartridge threadable to an actuator body in an actuator assembly for a disc drive. The disc drive has at least one rotating disc for storing information. The actuator assembly has an actuator body having a mounting opening with at least a portion of the mounting opening being threaded and a bearing cartridge having an outer surface with at least a portion of the outer surface being threaded. The bearing cartridge is threadably received within the mounting opening of the actuator body thereby releasably securing the actuator body to the bearing cartridge. A method for securing an actuator body to a bearing cartridge in an actuator assembly of a disc drive is provided.